William Hill overtook Ladbrokes yesterday to become the UK's biggest betting shop owner, taking its total number of shops to 2,237 after buying Stanley Leisure's 624 shops for £504m.

William Hill overtook Ladbrokes yesterday to become the UK's biggest betting shop owner, taking its total number of shops to 2,237 after buying Stanley Leisure's 624 shops for £504m.

Its shares fell 3 per cent to 510.5p on fears the company has overpaid for Stanley's shops. There was also disappointment that the capital William Hill had promised to return to shareholders will be retained as a result of the acquisition.

David Harding, the chief executive of William Hill, defended the price. "It is a full price but it is fair given the strategic benefits it will bring," he said. "Stanley's shops are less profitable than ours but that is the opportunity for us - to improve on its performance."

Up to 50 shops may be sold off to alleviate competition concerns.

Speculation is mounting that Stanley, now a pure casino operator, will merge with its rival, London Clubs International (LCI). Genting, a Malaysian gaming operator, has amassed stakes of 20 per cent in Stanley and 29.9 per cent in LCI over the past year, sparking rumours that it is planning to combine the two.

But Bob Wiper, the chief executive of Stanley, said there were no plans to merge with LCI.